To examine the trichloroethylene (C2HCl3)-degrading capability of five microorganisms, the maximum rate, extent, and degree of C2HCl3 mineralization were evaluated for Pseudomonas cepacia G4, Pseudomonas cepacia G4 PR1, Pseudomonas mendocina KR1, Pseudomonas putida F1, and Methylosinus trichosporium OB3b using growth conditions commonly reported in the literature for expression of oxygenases responsible for C2HCl3 degradation. By varying the C2HCl3 concentration from 5 microM to 75 microM, Vmax and Km values for C2HCl3 degradation were calculated as 9 nmol/(min mg protein) and 4 microM for P. cepacia G4, 18 nmol/(min mg protein) and 29 microM for P. cepacia G4 PR1, 20 nmol/(min mg protein) and 10 microM for P. mendocina KR1, and 8 nmol/(min mg protein) and 5 microM for P. putida F1. This is the first report of these Michaelis-Menten parameters for P. mendocina KR1, P. putida F1, and P. cepacia G4 PR1. At 75 microM, the extent of C2HCl3 that was degraded after 6 h of incubation with resting cells was 61%-98%; the highest degradation being achieved by toluene-induced P. mendocina KR1. The extent of C2HCl3 mineralization in 6 h (as indicated by concentration of chloride ion) was also measured and varied from 36% for toluene-induced P. putida F1 to 102% for M. trichosporium OB3b. Since C2HCl3 degradation requires new bio-mass, the specific growth rate (mu max) of each of the C2HCl3-degradation microorganisms was determined and varied from 0.080/h (M. trichosporium OB3b) to 0.864/h (P. cepacia G4 PR1).